Missense mutations in copper-zinc superoxide dismutase (SOD1) are linked to autosomal- dominant, adult-onset, familial amyotrophic lateral sclerosis (FALS). The principal investigators of this application plan a concerted,synergistic approach to determine how these SOD1 mutations relate to ALS. Dr. J.S. Valentine's laboratory has a long track record in the study of SOD1 metallobiochemistry. Dr. P.J. Hart's laboratory has over 10 years experience in 3-D structure and function studies of normal and pathogenic SOD1. Dr. D.R. Borchelt has an established track record in using transgenic mice to study mechanisms of SOD1-linked FALS. Together, we will use a three- pronged approach to dissecting the toxic mechanism(s) of mutant SOD1 - chemistry (Project 1),3- D structure and solution biophysical properties (Project 2), and disease-specific function (Project 3). To support these projects, we will have a Core that provides analytical support in the form of proteomics, mass spectrometry, and ICP-MS metal analysis. Our general approach is to characterize SOD1 proteins encoding novel mutations that target a particular chemical or structural feature of the protein. After thorough in vitro characterization, we will examine, in vivo, the ability of these novel SOD1 proteins to cause motor neuron disease. The Project goals are to: 1) understand the role of oxidative chemistry in both direct and indirect modes of toxicity to motor neurons;2) understand the consequences of oxidative damage to SOD1 on its structure and its solution properties;3) determine the structural elements in SOD1 that predispose it to produce non-native homo- (or hetero-) polymeric interactions, and to understand their role in toxicity to motor neurons; and 4) understand the causes and consequences of mutant SOD aggregation by characterizing the SOD1 protein that is found within these aggregates as well as by characterizing other proteins that may be contained within these structures. Through our combined efforts we will be able to define structure and disease-function relationships at an unprecedented level.